The formyl peptide receptor is involved in the activation of polymorphonuclear leukocytes (PMN) and their subsequent response to certain chemotactic stimuli. Its role in chemotaxis involves the binding of chemotactic peptides such as N-formyl--1-methionyl-1-leucyl-1-phenylalanine (FMLP), and presumably, some message transmission from the outside to the inside of the cell. In this project, we propose to define and characterize the structural and functional characteristics of the human formyl peptide receptor. This will be accomplished by constructing peptide and epitope maps of purified receptor, using polypeptide hydrolysis and enzymatic cleavage, monoclonal antibodies, and bifunctional photoaffinity reagents. A monoclonal antibody library will be prepared against different epitopes of the purified receptor; priority of study will be given to those antibodies that have some functional effect on the cell, such as inhibition/activation of chemotaxis, inhibition of FMLP binding, etc., because these antibodies may recognize some functional domains of the receptor. Therefore, biological assays will parallel all biochemical procedures. Products from the hydrolysis and cleavage will be used in Western blots to define characteristics of the epitopes the "functional" antibodies recognize. Photoaffinity reagents will be used to radioiodinate the binding site of the receptor; radioiodinated components will then be separated by two-dimensional polyacrylamide gel electrophoresis. The information obtained from this study may elucidate the components and mechanisms involved in FMLP binding and recognition, chemotaxis, and cell motility in general. In understanding the structural and functional arrangement of the receptor, the long term goal of this project is to compare normal receptor with receptor from chemotactically defective neutrophils, and to associate any structural differences between the two with the chemotactic defect itself, and with certain diseases such as localized juvenile periodontitis.